Predictive tool of seagrass health to optimize the design of low crested structures in the Mediterranean Sea

Project Information

SEGRALCS

Grant agreement ID: 101109919

DOI

10.3030/101109919

Project terminated on 1 January 2025

EC signature date 24 March 2023

Start date 1 May 2023

End date 31 October 2025

Funded under

• Marie Skłodowska-Curie Actions (MSCA)

Total cost

No data

EU contribution

€ 206 641,20

Coordinated by

UNIVERSITAT POLITECNICA DE VALENCIA
Spain

Periodic Reporting for period 1 - SEGRALCS (Predictive tool of seagrass health to optimize the design of low crested structures in the Mediterranean Sea)

Reporting period: 2023-05-01 to 2025-10-31

Summary of the context and overall objectives of the project

Coastal erosion poses a global threat to people, economies, and ecosystems, including valuable ecosystems, such as seagrass meadows. In Europe, the presence of coastal defence structures, such as low-crested structures (LCS), can modify water and sediment flow, potentially harming seagrasses. Incorporating ecological impact criteria into their design is a challenging task that requires a careful consideration of potential harm. The MSCA-funded SEGRALCS project aims to develop a quantitative prediction tool designed to assist civil engineers and decision-makers in optimising the ecological design of breakwaters. It will reduce uncertainty related to the environmental performance of breakwaters, ultimately contributing to the conservation and preservation of seagrasses throughout their lifetime. The project focus on two seagrass species found in the Mediterranean Sea, namely Cymodocea nodosa and Posidonia oceanica. Additionally, the project aims to establish design guidelines for building more sustainable and eco-friendly concrete blocks to protect the coastline.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

A compilation of data on the effects of hydromorphological threats on Posidonia oceanica and Cymodocea nodosa seagrass species was conducted. A literature review was carried out to determine specific parameters for defining, on the one hand, the hydrodynamic impact and, on the other hand, the morphological impact. Regarding the hydrodynamic impact, the maximum hydrodynamic conditions that seagrasses can withstand in a given area are reflected in the position of the upper limit of these meadows. Data for defining this upper meadow limit were extracted from the literature. Velocities that favour seagrass growth and thresholds above which uprooting of plants may occur were also identified in the literature. Additionally, the importance of maintaining minimum velocities above a certain threshold to prevent a decrease in internal oxygen levels as the flow velocity decreases was highlighted. A literature review was also conducted on numerical models to estimate the hydrodynamics on the position of seagrass meadows. These models serve as valuable tools to enhance the understanding of hydrodynamic and morphological conditions affecting seagrasses in specific areas.
Regarding morphological impacts, damage functions for burial and erosion levels were developed for different seagrass species using data from laboratory experiments and field studies available in the literature. The search was extended to all seagrass species worldwide. The species included in the analysis were Cymodocea nodosa, Cymodocea serrulate, Posidonia oceanica, Zostera noltii, Zostera marina, Halophila ovalis, Halodule uninervis, and Syringodium isoetifolium. Burial and erosion thresholds for 50% and 100% mortality of shoots were extracted. At 50% mortality, some species showed the capacity to recover from these impacts, whereas at 100% mortality, shoot death was observed to be independent of the duration, frequency or timing of events. The results of this project can also be applied to the design of sand fills to conserve adjacent seagrasses by gradually distributing sand across the beach profile and avoiding burial levels that exceed the identified mortality thresholds.
Additionally, literature data on the design of breakwater armour units were compiled and analyzed to identify design criteria that optimize the ecological function of breakwaters and reduce the carbon footprint of concrete production. Implementation barriers that need to be addressed for effective implementation and broader adoption of more sustainable and multifunctional coastal defences were also proposed.
The participation in leading national and international coastal engineering conferences allowed for the dissemination of results and engagement with the scientific community interested in innovative advances related to Nature-based Solutions, and engineering consultancies as end-users of the project results to integrate them into their projects. The dissemination of results at conferences and during the secondment also facilitated collaborations with researchers working in the same field.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The methodology underlying the predictive tool is expected to have a significant scientific impact, given the growing importance of seagrass bed protection. The developed damage functions and mortality thresholds, along with the methodology designed to improve the understanding of the hydrodynamic and morphological factors affecting seagrass meadows at specific sites, are of great interest to the scientific community working on Nature-Based Solutions (NbS) for the efficient design and monitoring of LCS systems. Additionally, the project proposes design criteria to ecologically improve breakwaters’ design to promote biocolonization and reduce the environmental footprint of concrete production while preserving structural integrity.
The project contributes to the conservation of seagrasses, which play an important role in cleaning and improving the quality of water in coastal regions. The construction of breakwaters also benefits to society as beach users and protects the population settled in the coastal zone from extreme hydrometeorological events.

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